What is contrast-enhanced ultrasound? What diseases can it detect?

Author: He Wen, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Reviewer: Gao Xianshu, Chief Physician, Peking University First Hospital

Ultrasound medicine is an important part of clinical medicine, which covers ultrasound diagnosis and interventional ultrasound. In recent years, the application of some new technologies has greatly improved the level of ultrasound diagnosis and treatment, one of which is ultrasound angiography.

1. What is the general process of ultrasound contrast examination?

Ultrasound contrast imaging improves the display of microblood flow and low-speed blood flow through the scattering enhancement of ultrasound contrast agents, making up for the shortcomings of conventional ultrasound and greatly improving its precision and accuracy.

There are many types of contrast agents. Now there are second-generation and third-generation contrast agents that are harmless to the human body. They can be exhaled out of the body through the lungs in a few minutes and are generally metabolized within 15 minutes.

Currently, there are no absolute contraindications to the use of ultrasound contrast agents. Patients with renal failure or renal insufficiency can also use them. Patients who are allergic to contrast agents should be cautious. There are no other special requirements.

Before ultrasound contrast imaging, the patient's medical history should be inquired about, including any history of allergies or other conditions that cannot be treated with ultrasound contrast imaging. After the inquiry, an intravenous channel should be established, and a needle should be inserted into the vein to inject contrast agent. The time, intensity, and time of contrast agent entering the organ should be observed, and the disease can be diagnosed and judged based on the enhancement.

Figure 1 Original copyright image, no permission to reprint

The entire process of ultrasound angiography takes only 3-5 minutes. If it is an observation study, it will take about 10 minutes. There is generally no discomfort during the whole process. In some cases, the face will turn red and there will be palpitations. It is very rare for anaphylactic shock to occur. If allergic symptoms occur, we also have emergency measures to deal with it.

After completing the ultrasound angiography and analyzing the images, a report can be issued. Generally, the results can be obtained within 5 minutes.

2. What diseases can be examined by ultrasound imaging?

First of all, solid organs, such as the liver, kidney, thyroid gland, breast, and uterus, can all be examined with ultrasound contrast imaging. For tumor lesions in solid organs, ultrasound contrast imaging can be used for differential diagnosis, to understand the microperfusion of the tumor, and to distinguish between benign and malignant tumors through the perfusion situation. This is currently the most widely used method.

Vascular diseases, such as intracranial blood vessels, neck blood vessels, large chest blood vessels, abdominal blood vessels, and limb blood vessels; arteriosclerosis stenosis, dissecting aneurysms, and other inflammatory lesions can be diagnosed through conventional ultrasound, but sometimes there are shortcomings. For example, in the case of carotid artery plaque, conventional ultrasound can understand the location, size, presence of ulcers, and the degree of stenosis of the blood vessels. However, because the new blood vessels in the plaque lack the support of basement membrane and connective tissue, they are very fragile and easy to rupture. Conventional ultrasound technology is still limited in displaying the new blood vessels in the plaque. Ultrasound angiography can accurately show the number, distribution and density of new blood vessels in the plaque. Combined with conventional ultrasound, it can accurately judge the stability of the plaque.

In addition, conventional ultrasound display is relatively limited for the starting segments of the carotid artery, vertebral artery, and subclavian artery, as well as intracranial blood vessels. Ultrasound angiography can greatly improve the display rate of blood vessels and make judgments on vascular diseases.

Ultrasound angiography can also show venous thrombosis, providing a basis for clinical venous stroke; intracranial aneurysms, including some other tumor lesions, can also be diagnosed through ultrasound angiography.

In terms of the heart, ultrasound angiography has also solved many clinical problems. Conventional ultrasound can detect cardiac thrombus, tumors and other lesions, which are difficult to identify. Ultrasound angiography can quickly identify whether it is a thrombus or a tumor; for some congenital heart diseases and acquired heart diseases, ultrasound angiography can greatly improve the diagnosis rate; in addition, ultrasound angiography can understand the perfusion of the ventricular wall, including the formation of ventricular aneurysm, providing a basis for diagnosis; for the condition of the endocardium, ultrasound angiography can show it more clearly.

For trauma, it is very important to make a quick and accurate diagnosis. Conventional ultrasound can determine whether there is fluid accumulation in the abdominal and thoracic cavities, and whether there are organ ruptures, but it is easy to miss some active bleeding or minor injuries. Ultrasound angiography can accurately show whether there is active bleeding and some minor injuries, and can accurately diagnose organ injuries, providing a basis for clinical diagnosis and treatment.

Ultrasound medicine can not only diagnose diseases, but also perform interventional treatments, such as ultrasound-guided puncture biopsy and ultrasound-guided tumor ablation therapy.

3. What are the advantages of tumor puncture biopsy and ablation treatment under the guidance of ultrasound angiography?

Various imaging examinations have revealed space-occupying lesions in organs. Sometimes it is difficult to determine the nature of the lesions. Even if it is considered to be malignant, the pathological classification cannot be determined. In this case, precise puncture biopsy can be performed under ultrasound guidance to perform pathology to confirm the diagnosis.

We know that some tumors can undergo non-liquefactive necrosis or have some inflammatory lesions around them. If the surrounding inflammatory tissue or necrotic area is obtained during the puncture biopsy, the pathology report will be inaccurate. Taking a biopsy under the guidance of ultrasound contrast imaging can greatly improve the accuracy of the puncture, puncture the active area of ​​the tumor, avoid the necrotic area, and distinguish the surrounding inflammatory lesions, greatly improving the positive rate of puncture biopsy.

Figure 2 Original copyright image, no permission to reprint

Ultrasound angiography also plays a very important role in tumor ablation therapy. It can accurately guide the ablation of the active area of ​​the tumor during the operation and determine whether the tumor is completely ablated. If it is not completely ablated, ablation can be performed again. This can eliminate the tumor to the greatest extent and reduce the residual.